The present invention relates to liquid crystal display devices in which a reflector and coloring layers are provided on a surface of a substrate at a liquid crystal layer side, electronic apparatuses provided with the liquid crystal display devices, and substrates for use in the liquid crystal display devices.
Hitherto, due to low power consumption characteristics, reflective liquid crystal display devices have been used for mobile information terminals and the like. In particular, concomitant with the recent increase in the communication of image information, movement towards color reflective liquid crystal display devices is in progress.
In liquid crystal display devices, by providing a reflector on an exterior surface or an interior surface of a liquid crystal layer, a reflective liquid crystal display device can be constructed. However, it is believed that the reflector is preferably provided on the interior surface of the liquid crystal layer since decrease in display quality, such as double images by parallax and color blurring, can be avoided. For example, in active matrix liquid crystal display devices, when pixel electrodes are also used as a reflector by providing reflective properties to the pixel electrodes formed at a substrate provided with switching elements, a reflective color liquid crystal display device can be realized in which decrease in display quality can be avoided.
Recently, in order to ensure visibility in dark environments, there is a proposal in which a transflective liquid crystal display device capable of performing both reflective display and transmissive display is constructed by forming a reflector which not only reflects light but also transmits light. According to the transflective liquid crystal display device as described above, reflective display is performed in normal conditions in which power consumption is low, and when necessary, transmissive display is performed in dark environments, whereby visibility can be ensured.
However, in an arrangement in which pixel electrodes are also used as a reflector, aluminum generally used as a reflector is exposed in manufacturing steps. Since aluminum has poor corrosion resistance, as is well known, in the arrangement described above, damage will be done to the aluminum, and hence, reflective properties as a reflector and electrical properties as electrodes may be degraded in some cases.
For example, among manufacturing processes for liquid crystal display devices, a process for forming an alignment film includes a step of coating a solution primarily composed of a polyimide resin or a polyamic acid dissolved in a polar solvent, such as N-methyl pyrrolidone (1-methyl-2-pyrrolidinone) or xcex3-butyrolactone (4-hydroxy butyric acid xcex3-lactone) and a following step of heating to 150 to 250xc2x0 C. Accordingly, the probability of damaging the aluminum is high.
In addition, when the other electrodes opposing the reflective electrodes are formed of ITO (Indium Tin Oxide), a difference in polarity is generated between the aluminum electrode and the ITO electrode with the liquid crystal layer provided therebetween, and hence, long term reliability of the liquid crystal display device and display quality thereof are both degraded. These phenomena described above also occur when an aluminum alloy containing other atoms is used, even though the degree thereof may be different to some extent.
In the transflective liquid crystal display device described above, when transmissive display is performed, the contrast ratio is significantly decreased by light leakage from areas other than pixels, and hence, high quality display cannot be performed. In order to prevent a decrease in the contrast ratio due to light leakage, a shading layer may be additionally provided on a substrate opposing a substrate provided with a reflector, i.e., a substrate closer to an observer.
As a shading film, chromium or a black resin material is usually used. Among the materials mentioned above, chromium has high shading properties and can be formed to a thickness of 200 nm or less; however, since chromium is a metal material, the surface reflectance thereof is high. For example, the reflectance of monolayer chromium is high, such as approximately 60%, and the reflectance of low reflectance two-layer chromium is approximately 7%. Accordingly, when chromium is used for a shading film, since light incident from the observer side reflects at the surface of the shading film, there is a problem in that the contrast ratio in reflective display is decreased.
On the other hand, since a black resin material has a low reflectance, surface reflectance can be suppressed; however, since the shading properties of the black resin material is poor, in order to maintain an optical density of 2 or more which is required for transmissive display, the black resin material must be formed to be thick. Consequently, there are problems in that the flatness of the substrate is degraded, and since patterned width cannot be small, the opening area ratio is decreased as a result.
In consideration of the situation described above, the present invention is completed, and an object thereof is to provide a liquid crystal display device having superior reflective properties and high display quality, an electronic apparatus, and a substrate for use in the liquid crystal display device.
To these ends, the liquid crystal display device according to a first invention having a liquid crystal layer provided between a first transparent electrode formed at a first substrate side and a second transparent electrode formed at a second substrate side, comprises a reflector formed on a surface of the second substrate at the liquid crystal layer side so as to reflect at least light incident from the first substrate side, a shading film formed above the surface at the second substrate at the liquid crystal layer side so as to have an opening area corresponding to an intersection area at which the first transparent electrode and the second transparent electrode intersect each other, and a coloring layer formed above the surface of the second substrate at the liquid crystal layer side so as to cover the shading film.
According to the first invention, since the liquid crystal layer is provided between the first and the second transparent electrodes composed of the same type of material, the display quality and the long-term reliability of the liquid crystal display device are not degraded. In addition, on the reflector, since the shading film and the coloring layer are formed, so that the reflector is not to be exposed. Accordingly, in a manufacturing process of the liquid crystal display device, since the reflector will not be exposed to chemical reagents, gases, liquid crystal, and the like, damage done to the reflector can be avoided. Furthermore, since the coloring layer is formed so as to cover the shading film, the surface reflection at the shading film can be suppressed, and in addition, an optical density required for the shading film can be less. In particular, since light passes through the shading film twice in reflective display, even if the optical density is less, sufficient shading properties in practical use can be obtained when reflective display is primarily performed.
In the first invention, in the opening areas in the shading film, the reflector is preferably provided with first openings at which light passes therethrough. In the structure mentioned above, since the reflector will not function as an electrode, that is, since liquid crystal layer even at the first openings in the reflector is driven by the second transparent electrode, transmissive display can be performed by light passing through the openings. In transmissive display, since light is not determined by the opening areas in the shading film but is determined by the first openings provided in the reflector, an optical density required for the shading film can be determined only in consideration of reflective display.
In the first invention, the structure is preferable in which a first film is provided between the reflector and the surface of the second substrate at the liquid crystal layer side. According to the structure mentioned above, even if the adhesiveness between a metal material used as the reflector and the surface of the second substrate is inferior, the adhesiveness of the reflector can be improved by the first film. As the first film that improves the adhesiveness of the reflector, metals, oxides, and nitrides can be used. As the metals, transition metals included in Groups Vb to VIb, such as Ta, Cr, Mo, and W, are mentioned. As examples of the oxides, oxides of the transition metals mentioned above, such as Ta2O5, silicon oxides such as SiO2, and the like are mentioned, and as other examples of the oxides, TiO2, ZrO2, SiO2 optionally combined with the oxides mentioned above, Al2O3, and the like are mentioned. In addition, as examples of nitrides, silicon nitrides represented by Si3N4 are mentioned. Since the first film is used for improving adhesiveness of the reflector, a thickness of approximately 100 nm or, depending on the case, 30 to 60 nm is sufficient. In addition, when a film having no conductance, such as a SiO2 film or a Ta2O5 film, is used, since the first film may remain over the entire surface of the second substrate, the first film may not be patterned. For example, when silver or an alloy primarily composed of silver is used as the reflector, and when glass is used as the second substrate, a film composed of Mo, Ta2O5, SiO2, or the like is preferably used as the first film which improves adhesiveness. When a substrate having flexibility, such as a plastic film, is used as the substrate, a SiO2 film, TiO2, ZrO2, SiO2 optionally combined these oxides mentioned above, or the like is preferably used as the first film.
In the first invention, the shading film is preferably composed of a black resin material. As the black resin material mentioned above, for example, a color resist containing a black pigment dispersed therein and a printable black painting material are mentioned. The black resin material described above is superior to chromium in terms of low reflectance but is inferior thereto in terms of shading properties. However, in the first invention, since the optical density of the shading film can be less as described above, the shading film need not be formed thick. For example, when transmissive display is only considered, an optical density of 2 or more is required for the shading film, and in order to achieve the optical density mentioned above by a black resin material, a thickness of approximately 0.9 xcexcm is required. On the other hand, in the first invention, since the coloring layer is formed so as to cover the shading film, light passes through the shading film twice, and light is determined by the first openings in the reflector in transmissive display, the thickness required can be 0.5 xcexcm or less even when a black resin material is used for the shading film, that is, the thickness thereof can be decreased by approximately half. Accordingly, in the first invention, when a black resin material is used for the shading film, the flatness of the substrate is not degraded, and the opening area ratio is not decreased. In this connection, in general, since the contrast ratio of a reflective liquid crystal display device is approximately 1:10 to 1:25, and this ratio is less than that of transmissive liquid crystal display device, the optical density can be decreased in accordance with a liquid crystal display mode to be used, and the thickness of a black resin material can be even decreased.
In the first invention, the shading film is preferably formed by laminating the coloring layers of at least two colors. According to the shading film mentioned above, an additional film need not be formed as the shading film, and hence, cost reduction can be performed. Since the density of a coloring layer for use in a common reflective liquid crystal display device is low compared to that for use in a transmissive liquid crystal display device, even if coloring layers of at least two colors are laminated with each other, the optical density thereof may be 1 or less in some cases, and hence, a required optical density is difficult to obtain. On the other hand, in the arrangement described above, since light in reflective display passes through the shading film twice which is formed by laminating coloring layers of at least two colors, and since light in transmissive display is determined by the first openings in the reflector, sufficient shading properties can be obtained even if coloring layers having low color densities are used. For example, when there are coloring layers having colors, R (red), G (green), and B (blue), and when the optical density of the shading film is 0.7 which is formed by laminating these coloring layers of three colors, the practical optical density is approximately 1.4 since light passes therethrough twice, and hence, sufficient shading properties in practical use can be obtained for a reflective liquid crystal display device generally having a contrast ratio of 1 to 25 or less.
In addition, in the case in which the shading film is composed of the coloring layers of at least two colors, a coloring layer having high color density may be provided at parts of the opening areas in the shading film at a certain ratio, and an average density of light reflected and colored in the opening areas in the shading film may be set to be a value preferable in reflective display. In the arrangement described above, since an area at which coloring layers having high color densities are laminated with each other is used as the shading film, the optical density of the shading film can be even increased. For example, when an optical density is 1.6 at an area at which coloring layers of three colors are laminated with each other, since a practical optical density thereof reaches approximately 3.0 due to light passing through the shading film twice, reflective display can be performed which has a high contrast ratio of 1 to 100 or more.
In the first invention described above, the optical density of the shading film (by light passing once) is preferably 0.5 to 1.7. The reason for this is that, in the first invention, since light passes through the shading film twice in reflective display, as described above, even if the optical density thereof is less, the practical optical density (by light passing twice) is increased.
In the first invention, it is preferable that, with respect to the intersection area of the first transparent electrode and the second transparent electrode, the opening area in the shading film be expanded toward the outside from the periphery of the intersection area by at most approximately a half of the distance between the first transparent electrode and the second transparent electrode.
In a liquid crystal display device, a pixel in a design is an area at which the first transparent electrode and the second transparent electrode intersect each other in plan view; however, there is an area outside the pixel in the design at which liquid crystal molecules are driven by an oblique electric field. In particular, it was confirmed by the inventor of the present invention that liquid crystal molecules in a specific area was driven by an oblique electric field, in which the specific area was in areas of the first and the second transparent electrodes and was outside the intersection area thereof by approximately half of the distance (thickness of the liquid crystal layer) between the electrodes from the periphery of the intersection area. For example, when the distance between electrodes is 4.0 xcexcm in some liquid crystal display mode, liquid crystal molecules are driven which are in an area extending toward the outside from the edge of the electrode by approximately 2.0 xcexcm. Accordingly, when the opening area in the shading film is expanded to an area corresponding to the area described above so that the reflector reflects light, the practical opening area ratio can be increased.
For example, in the case of a liquid crystal display device employing a normally black liquid crystal display mode in which black display is performed when no voltage is applied, when white display is performed by applying voltage, even in an area which is outside the periphery of the pixel in a design to some extent, the liquid crystal molecules in the area are driven by an oblique electric field. Accordingly, by disposing the reflector at the area mentioned above without providing the shading film, an area functioning as a pixel in practice is increased more than that of the pixel in the design, whereby the opening area ratio is increased, and bright display can be realized.
On the other hand, even in the area of the pixel in the design, there is an area at which liquid crystal molecules are not driven by an oblique electric field. In the area mentioned above, when the shading film is provided so that light is not reflected by the reflector, decrease in contrast ratio can be avoided. For example, in a liquid crystal display device employing normally white display mode in which white display is performed when no voltage is applied, when the reflector is disposed at an area at which liquid crystal molecules are not driven without providing the shading film, since a completely black display cannot be performed even when black display is performed by applying voltage, the contrast ratio is decreased. However, when the shading film is provided so as to cover the area described above, decrease in contrast ratio can be avoided.
In addition, in the case of a liquid crystal display device employing a normally white liquid crystal display mode using super twisted nematic (STN) liquid crystal, the contrast may be decreased in some cases due to a phenomenon in which, even when black display is performed in a pixel, an area remains at which liquid crystal is not totally driven at some side of the periphery of the pixel in a design by an effect of an oblique electric field. However, when the reflector and the electrode are separately provided, as is the case with the first invention, decrease in contrast ratio can be avoided by covering the area described above by the shading film. Furthermore, when the reflector is disposed without providing the shading film at the area at which liquid crystal molecules are driven by an oblique electric field even though they are outside the pixel, the practical opening area ratio is increased, and hence, bright display can be performed.
The prevention of decrease in contrast ratio and the practical increase in opening area ratio described above can first be achieved by separately providing the reflector and the pixel electrode, as described in the first invention. Accordingly, description of the points described above will again be made with reference to figures. FIG. 19A is a schematic plan view showing a passive matrix liquid crystal display device using STN liquid crystal, FIG. 19B is a view showing an aligned direction of liquid crystal molecules in the vicinity of the substrate and an aligned direction of bulk liquid crystal molecules in the liquid crystal layer. FIG. 19C is a schematic cross-sectional view taken along the line GG-GGxe2x80x2 in FIG. 19A when no voltage is applied, and FIG. 19D is a schematic cross-sectional view taken along the line GG-GGxe2x80x2 in FIG. 19A when a voltage is applied.
As shown in FIG. 19A, in a passive matrix liquid crystal display device, an area at which a transparent electrode 22 provided at an upper substrate 21 and a transparent electrode 32 provided at a lower substrate 31 opposing each other intersect each other in plan view is an area 50 of a pixel in a design. As shown in FIG. 19B, the case is assumed in which a counterclockwise STN liquid crystal display mode is employed by a combination of a rubbing direction 23 at the upper substrate 21 and a rubbing direction 33 at the lower substrate 31. In this case, liquid crystal molecules 41 in the vicinity of the upper substrate 21 are aligned along the rubbing direction 23 at the upper substrate 21, and liquid crystal molecules 42 in the vicinity of the lower substrate 31 are aligned along the rubbing direction 33 at the lower substrate 31, and bulk liquid crystal molecules 43 in a liquid crystal layer 40 are aligned so as to be orthogonal to the direction in which electrodes 32 at the lower substrate 31 are formed.
When no voltage is applied, as shown in FIG. 19C, bulk liquid crystal molecules 43 in the liquid crystal layer 40 consistently align, and when a voltage is applied, as shown in FIG. 19D, electric flux lines 53 generated between the electrodes 22 at the upper substrate 21 and the electrodes 32 at the lower substrate 31 are distorted at the peripheries of the pixels (that is, generation of xe2x80x9coblique electric fieldxe2x80x9d), the alignment of the bulk liquid crystal molecules 43 in the liquid crystal layer 40 fall into disorder at one edge of each pixel 53, whereby reverse tilt domains are generated, and areas 51 appear at which the bulk liquid crystal molecules 43 are not normally driven. On the other hand, at the other side of the electrode, areas 52 appear at which the bulk liquid crystal molecules 43, which are even outside the electrodes 32 at the lower substrate 31, are driven.
Accordingly, when the shading layer is formed so as to extend to areas corresponding to the areas 51 at which liquid crystal molecules 43 are not normally driven, and when the reflector is formed without providing the shading film at areas corresponding to the areas 52 at which liquid crystal molecules 43 are normally driven, the practical opening area ratio can be increased without decreasing the contrast ratio, whereby bright display can be performed. Improvement in performances described above cannot be realized by a conventional structure in which electrodes are provided with reflective properties, and it can first be realized by forming the reflector separately from the pixel electrodes, as described in the first invention.
In the first invention, as the reflector, an alloy primarily composed of aluminum, silver, chromium, or the like, or a metal can be used. When an alloy primarily composed of aluminum is used as a reflector, a reflector having high reflectance can be realized at a lower manufacturing cost. In this case, the content of aluminum in the alloy is preferably 80 wt % or more. In addition, when an alloy primarily composed of silver is used as a reflector, significantly high reflectance can be realized. In this case, the content of silver in the alloy is preferably 80 wt % or more.
Furthermore, as the second substrate, a substrate having flexibility, such as a plastic film, can be used. When the substrate having flexibility mentioned above is used, a metal which can be formed by electroless plating, such as an alloy primarily composed of nickel, may be used as the reflector.
In the first invention, when a metal, which is used as a reflector, may be damaged by exposure thereof to chemical reagents and gases used in a step of forming a coloring layer, it is preferable that a second film, which covers at least the surface of the reflector, be further provided. In the arrangement mentioned above, it is preferable that the second film will not significantly decrease the reflectance of the reflector. In the first invention, since the coloring layer actually protects the reflector, it is sufficient for the second film described above to have resistance against chemical reagents, gases, and the like used in a step of forming the coloring layer. For example, when the coloring layer is formed on the reflector by a printing method or a dyeing method, a second film is not particularly required, and when the coloring layer is formed by a color resist method using a photosensitive color resist, since a strong alkaline developer may be used depending on materials to be used, the second film is preferably formed in accordance with a combination of a developer and a metal used for the reflector so as to cover the surface of the reflector.
However, when an aluminum alloy or a silver alloy is used as the reflector, the second film may be eliminated in some cases. For example, when an aluminum alloy containing 1 wt % neodymium is used for the reflector, since the corrosion resistance is improved, damage done to the reflector so as to decrease the reflectance will not occur by a developer having a general composition, such as a mixed aqueous solution of sodium carbonate and sodium hydrogencarbonate, or an aqueous solution of tetramethylammonium hydroxide, whereby the second film is not necessary to be provided.
In addition, for example, an aluminum alloy containing 3 wt % neodymium, or an aluminum alloy containing 3 wt % neodymium and 3 wt % titanium (Ti) is used for the reflector, corrosion resistance thereof is further improved, whereby the second film is not necessary to be provided.
Since the second transparent electrode must be formed on a surface having different properties, for example, glass or a resin material, the adhesiveness to these surfaces must be required to some extent. Accordingly, in the first embodiment, the second transparent electrode is preferably formed on a third film to improve the adhesiveness. As the third film, inorganic oxide films such as SiO2 are mentioned, and in particular, it is preferable that SiO2 and ITO to be used as the second transparent electrode be sequentially formed by sputtering or the like.
In the structure of the first invention in which the reflector is provided with the first openings, it is preferable that a fourth film formed so as to cover the coloring layer and a second opening in the coloring layer at the opening area in the shading film be further provided. According to the structure described above, color reproducibility both in reflective display and transmissive display can be optimized.
Alternatively, in the first invention, it is preferable that a fourth film formed so as to simply cover the coloring layer be further provided. By the fourth film mentioned above, since steps are planarized which are formed by the existence of the opening areas in the shading film and the coloring layer, and in addition, which are formed when there is the first openings in the reflector, degradation of display quality can be avoided.
The fourth film is preferably formed so as to have light scattering properties. According to the fourth film mentioned above, since the fourth film itself functions as a scattering layer, an additional scattering layer is not necessary to provide, and as a result, manufacturing steps can be reduced, and cost reduction can be performed.
As the fourth film described above, a resin material containing particles may be mentioned, in which the particles has refractive index different from that of the resin material and has diameters smaller than the thickness of the fourth film. Accordingly, a reflector having both flatness and scattering properties can be obtained.
As the resin material for the fourth film, acrylic resins or polyimide resins are mentioned, and as particles, inorganic particles, such as glass beads, and organic particles, such as polystyrene spherules, are mentioned. By the thickness of the resin material, difference in refractive indexes, particle diameters, and the degree of particle dispersibility, scattering properties can be controlled.
In the case described above, the haze value in the range of 40 to 90% and the difference in refractive indexes in the range of 0.05 to 0.12 are preferable. The refractive indexes of the resin material which can be used are, for example, approximately 1.50 for PMMA (polymethyl methacrylate), and approximately 1.60 to 1.65 for a polyimide resin, and the refractive indexes of particles which can be used are, for example, approximately 1.35 for PTFE (polytetrafluoroethylene), approximately 1.42 for PVDF (polyvinylidene fluoride), approximately 1.57 for LF1 optical glass, approximately 1.59 for styrene, approximately 1.62 for F2 optical glass, and approximately 1.65 for SF2 optical glass. By optional combination of materials described above, desired scattering properties can be obtained. The refractive indexes of the materials described above may have different values in accordance with manufacturing processes therefor and forms thereof. In addition, the materials described above are some of the materials that are usable, the first invention is naturally not limited thereto, and materials having various properties can be used by combination thereof.
In the first invention, the reflector is preferably formed on a roughened surface. According to the reflector mentioned above, since scattering properties are provided to the second substrate side, an additional scattering layer is not necessary to provide, whereby manufacturing steps can be reduced, and cost reduction can be performed. In addition, since the roughened surface is planarized by the fourth film, degradation of display quality caused by steps formed by the roughened surface can be avoided. For example, in order to provide scattering properties to the reflector, when roughened surface is formed which has a plurality of peaks and bottoms in which the difference thereof is 0.3 to 1.5 xcexcm, since the thickness of the liquid crystal layer or the pretilt angle of liquid crystal molecules partly varies depending on the shape of the roughened surface, superior display quality may not be obtained in some cases. However, as described above, since a planarized surface can be obtained by the fourth film, flatness of the second transparent electrode can be maintained. Accordingly, the arrangement thus described is effective for a TN (twisted nematic) mode having a twist angle of 100xc2x0 or less, and in particular, the arrangement is effectively combined with an STN mode which requires high precision in the thickness of the liquid crystal layer.
The roughened surface described above may be formed on a surface of a resin material formed on the surface of the second substrate at the liquid crystal layer side. As the resin material mentioned above, a photosensitive resin, such as an acrylic resin or a polyimide resin, can be effectively used. These materials have high temperature stability and can withstand processes for forming the reflector, the coloring layer, the second transparent electrode, and the like. Concerning photosensitivity, a negative and a positive type can both be used. In addition, a press method can be used in which a mold having a plurality of peaks and bottoms thereon is closely contacted on the surface of a coated resin material and is then pressed, and the roughened form is thereby transferred.
Furthermore, the roughened surface may be formed by performing a roughening treatment on the surface of the second substrate at the liquid crystal layer side. As the roughening treatment, there may be mentioned, for example, a method for coating and baking a sol-gel solution having particles dispersed therein, and a method for unevenly etching the surface of the substrate. In particular, when the second substrate is a glass substrate, there are several mentioned which may be used. For examples, there may be mentioned a first method for, after forming an oxide film on the surface of the substrate, unevenly etching the oxide film using the heterogeneous composition thereof, a second method of uneven etching using an etchant so as to dissolve parts of the substrate at which aluminum, boron, sodium, and the like exist at high concentrations contained therein, and a third method of uneven etching by an LPD (liquid phase deposition) method in which substrate components are precipitated by immersing the substrate in a supersaturated aqueous hydrofluoric acid solution. Among the methods described above, since the second and the third methods do not require steps of coating and sputtering and can only be performed by immersion in chemical solutions, they are advantageous in reducing cost.
In electronic apparatuses provided with the liquid crystal display devices of the first invention, bright and high quality reflective display can be performed, and in addition, since transmissive display can be performed when necessary, superior visibility can be obtained in various environments.
The objects described above can be achieved by the second substrate side in the liquid crystal display device of the first invention. That is, a substrate for a liquid crystal display device according to a second invention is a substrate opposite to the observer side of a pair of substrates for a liquid crystal display device, in which the pair of substrates have a liquid crystal layer provided therebetween. The substrate described above comprises a reflector formed on the substrate at the liquid crystal layer side so as to reflect at least light incident from the observer side, a shading film formed above the substrate at the liquid crystal layer side so as to have opening areas above the reflector, a coloring layer formed above the substrate at the liquid crystal layer side so as to cover the shading film, and a transparent electrode formed above the coloring layer.
According to this second invention, since the liquid crystal layer is provided between the same type transparent electrodes by adhering the substrate at the observer side and the second substrate, display quality and long-term reliability of the liquid crystal display device are not degraded. In addition, since the shading film and the coloring layer are formed on the reflector, damage done to the reflector can be avoided. Furthermore, since the coloring layer is formed so as to cover the shading film, surface reflection at the shading film is suppressed, and in addition, the optical density required for the shading film can be decreased.
In the second invention, the reflector is preferably provided with first openings so as to allow light to pass therethrough in the opening areas in the shading film. According to the reflector described above, since the reflector does not function as an electrode, that is, since the liquid crystal layer is driven by the transparent electrode even at the first openings in the reflector, transmissive display can be performed by light passing the first openings. In addition, in transmissive display, since light is not determined by the opening areas in the shading film but is determined by the first openings in the reflector, the optical density required for the shading film may be determined only by taking reflective display into consideration.
In the second invention, it is preferable that a first film is further provided between the reflector and the surface of the second substrate at the liquid crystal layer side. According to the first film mentioned above, even if adhesiveness between a metal used for the reflector and the second substrate is inferior, the adhesiveness of the reflector can be improved by the first film.
In the second invention, the shading film is preferably composed of a black resin material, and the optical density thereof is preferably 0.5 to 1.7. According to the shading film mentioned above, even if the shading film is formed of a black resin material, flatness of the substrate is not degraded, and the opening area ratio is not decreased.
In addition, in the second invention, the shading film is also preferably formed by laminating the coloring layers of at least two colors, and the optical density of the shading film is preferably 0.5 to 1.7. According to the shading film mentioned above, an additional film is not necessary to be provided as the shading film, and as a result, cost reduction can be performed.
In the second invention, a second film is preferably provided so as to cover at least the surface of the reflector. According to the second film mentioned above, since a metal used for the reflector is not exposed to chemical reagents, gases, and the like in a step of forming the coloring layer, damage will not be done to the reflector.
In the second invention, the transparent electrode is preferably formed on a third film that improves adhesive properties. According to the third film mentioned above, the transparent electrode can maintain the adhesiveness thereof to a surface of glass, a resin material, or the like having different properties and can be formed thereon.
In the second invention, when the first openings are provided in the reflector, a fourth film is preferably formed so as to cover the coloring layer and a second opening is preferably provided in the coloring layer at the opening area in the shading film. Accordingly, color reproducibility in reflective display and in transmissive display can be optimized.
Alternatively, in the second invention, a fourth film is preferably formed so as to simply cover the coloring layer. According to the fourth film mentioned above, since steps are planarized, which are formed by the existence of the opening areas in the shading film and the coloring layer, and which are formed when there are the first openings in the reflector, degradation of display quality can be avoided.
The fourth film preferably has light scattering properties. According to the fourth film mentioned above, since the fourth film itself functions as the scattering layer, an additional scattering film is not necessary to be provided, and as a result, cost reduction can be performed by decreasing the number of manufacturing steps.
As the fourth film, a film may be mentioned which is composed of a resin material containing particles having a refractive index differing from that of the resin material and having diameters smaller than the thickness of the fourth film. Accordingly, a reflector having flatness and scattering properties can be obtained.
In addition, in the second invention, the reflector is preferably formed on a roughened surface formed on the substrate at the liquid crystal layer side. According to the reflector formed on the roughened surface, since the substrate itself also has scattering properties, an additional scattering film is not necessary to be provided, and as a result, cost reduction can be performed by decreasing the number of manufacturing steps. In addition, a roughened surface is planarized by the fourth film, degradation of display quality caused by steps formed by the roughened surface can be avoided.
As the roughened surface described above, there are mentioned a surface of a resin material formed on the surface of the substrate at the liquid crystal layer side, a surface obtained by a roughening treatment of the surface of the substrate at the liquid crystal layer side, and the like.